The Google Shopping Content Objective-C Library by Google can access API data to sell products on Google, list ads, drive traffic, and increase sales. Developers can interact with the JSON API, working with iOS 3+ and Mac OS X 10.5+. Available introduction and example applications.
Here is a follow up interview with Raj Kadam, CEO of Viralheat API whom we have interviewed on the Sentiment Analysis API here. In 2012, Viralheat had about 30 billion calls over all its' APIs. Viralheat just announced a new API called Human Intent API.